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Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Process SamplingProcess Sampling
Sentry Equipment Corporation
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
ObjectiveObjective
• Gain an understanding of the methods to obtain representative samples
• Review the fundamentals of gases, liquids and bulk solids
• Overview of analyzing methods• Review the integration of sampling
with on-line instrumentation
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Why do we sample?Why do we sample?
• Product mix characteristics– Examples: Particle size, bacteria
count, chemistry, etc.• Identify process variations• Process control• Environmental monitoring• Product quality assurance• Custody transfer
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
What kind of sample?What kind of sample?
• “True” overall average of the entire lot for one or many characteristics
• Representative sample– Characteristics of the sample equal
that of the entire lot or batch• Consistent, accurate, and repeatable
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
How to get a representative How to get a representative samplesample
• Follow protocol that gets a consistent, accurate, and repeatable sample
• Understand the material physical properties• Use techniques that have as little sample bias as
possible– Profile the process and sampling system (i.e..
Liquids, slurries, gases, bulk solids, etc.)• Reduce sample to sample variation• Sample methods and results must be repeatable
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Sampling ErrorsSampling Errors
• Process analysis is only as good as the quality and representivity of the sample itself
• Sampling errors are costly because they can lead to:– Unnecessary process changes– Additional analysis of more samples– Release of off-spec product to the
customers– Scrap of good material
• The Sampling Scapegoat
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
General Sampling PracticesGeneral Sampling Practices
• Understand the process and the sampling objective to help select the proper device– I.e. Gas concentration, liquid chemistry, bulk
solids particle size analysis• Determine the best sampler location• Take several increments and composite them to
form the “sample”– Composite Sample – A sample obtained by
combining several distinct sub-samples or increments
• Sample frequently enough to identify process cycles
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
• Typically includes dipping a cup or container into an open vessel or opening a spigot on a vessel that may be under pressure– May require the process to be
interrupted in order to sample
• This sampling technique is generally considered unsafe– Operator is exposed to any process or
environmental hazards
• Direct sampling introduces the ability for sample variations due to human error and sample contamination
Direct SamplingDirect Sampling
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Indirect SamplingIndirect Sampling
• Indirect sampling isolates the operator from the process hazards
• Maintains a closed system
• Sample integrity preserved
• Allows the process to be sampled during normal production cycle
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
A few general sampling A few general sampling practicespractices
• Mix the material prior to sampling (if possible)• Take several increments and composite them
to form the “sample”– Composite Sample – A sample obtained by combining
several distinct sub samples or increments
• Collect the sample in a container that will not react with the sample
• Sample frequently enough to identify process cycles
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
• Determine the correct size required for the sample
• Use a sampler and sampling process that removes bias
• Understand the process– Sampling practices may vary from process
to process
A few general sampling A few general sampling practices (cont.)practices (cont.)
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Three categories for Three categories for sampling variationsampling variation
• Process variations/cycles• Material variation• Tool and techniques
– Including sample handling
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Process VariationsProcess Variations
• Be aware that the process and its conditions may vary over time
• Examine the sampling results and the effects of sampling frequency
• Use the sampler and sampling system to verify the process
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Ways to reduce material Ways to reduce material variationvariation
• Determine the appropriate mass of the actual sample– Provides a better idea about the overall properties
of the lot
• Collect several increments from the lot and form a composite sample
• Condition the material prior to sampling– Mix the sample if possible– Control the temperature, pressure, flow, etc.– Control the particle size
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Product CharacteristicsProduct Characteristics
• Identification of the product characteristics is critical for obtaining a representative sample
• Every gas, liquid, and bulk solid has its own unique physical property
• Many processes contain entrained gases that can expand when decompressed– Venting provisions must be taken into account
• Bulk solid characteristics can be very unpredictable– Some may pack one moment and fluidize the next– Two grades of the same material may act
differently
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
• Mass Flow• Funnel Flow• Arching/Bridging• Rat-holing• Flooding• Segregation
Flow CharacteristicsFlow Characteristics
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Material PropertiesMaterial Properties
• Abrasive – Materials that wear, grind, or rub on the inside of the sampler or any moving part
• Arching/Bridging – Materials that tend to form a bridge-like structure
• Free-Flowing – Materials that generally flow under the influence of gravity without the aid of agitation
• Floodable – Materials that aerate to a point where they begin to flow like a liquid
• Hygroscopic – Materials that tend to absorb and retain moisture from the atmosphere
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Material PropertiesMaterial Properties
• Cohesive – Materials that tend to stick to itself• Adhesive – Materials that tend to adhere or
stick to components of the sampler• Friable – Materials that are easily pulverized or
broken apart • Static Generating – Materials that generate
static from friction on itself or within the sampler
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Bulk DensityBulk Density• Mass per unit of volume in powder form,
including the air trapped between the particles
• Measured in g/cc, kg/l, lb/ft3• Examples:
– Cake Mix = 44 lb/ft3 (0.705 g/cc)– Cement Powder = 85 lb/ft3 (1.361 g/cc)– Oats = 27 lb/ft3 (0.432 g/cc)– Parsley Flakes = 3 lb/ft3 (0.048 g/cc)– Sand = 99 lb/ft3 (1.586 g/cc)– Tungsten Carbide = 250 lb/ft3 (4.004 g/cc)
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Tools and TechniquesTools and Techniques
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Sampling ToolSampling Tool
• The sampling tool is critical for providing a representative sample– The sampler must assure the sample integrity is
preserved
• Understand the analysis requirements to help determine which sampler to choose
• Understand the process variables that may impact the sampler design
• The sampler should keep the operator safe from any process or environmental hazards
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Principle for correct samplingPrinciple for correct sampling
• Every part of the lot has an equal chance of being in the sample
• Integrity of the sample is preserved before, during, and after sampling– Oxidation, abrasion, evaporation, and
contamination are examples of improper handling– Vapor pressure is an important characteristic to
take into account when sampling– The measure of the tendency of a material to
form a vapor.
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Manual “Grab” SamplesManual “Grab” Samples
• Typically, manual grab sampling is a poor, but common practice because it is taken from the most accessible part of the batch/process– Exception is when the sampler is located in a
proper/acceptable sample point and other good practices are recognized
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Gas SamplingGas Sampling
• Maintain pressure and sample integrity
• Monitor H2S, VOCs, water content
• Speed loops and analyzers are common
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Liquid SamplingLiquid Sampling
• Control pressure, temperature, flow rate
• Monitor pH, DO, Sodium, conductivity, TOCs, chemistry, etc.
• On-line analysis is common
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Bulk Solids SamplingBulk Solids Sampling
• Material characteristics and flow properties vary
• Monitor moisture, particle size, shape, etc
• Difficult to analyze on-line– Material waste
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Bulk Solids SamplingBulk Solids Sampling
Point Sample
Strip Sample
Cross Cut Sample
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Point SamplersPoint Samplers• Takes a sample from a
point in the material stream
• Used when conducting chemical analysis or when material is homogenous
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Strip SamplersStrip Samplers
• Takes a sample from a narrow portion of the stream
• Used in situations where product segregation exists
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Cross Cut SamplersCross Cut Samplers
• Takes a cross-section of the entire product stream
• Provides the most representative sample, but requires a lot of headroom
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Types of Measurements and Types of Measurements and TechnologyTechnology
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Off, At and On-Line Off, At and On-Line
Lab Testing
Infrequent Samples sent to a remote location
At-Line
Sample removed and tested locally
On-Line
Frequent Sample analysis
conducted in real time
Off-Line
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
Measurements/AnalysisMeasurements/Analysis
• Particle Size• Moisture• Chemical
Composition• Surface Area• Shape• Temperature• Dissolved Oxygen
• Effusivity• NIR• IR• Laser Induced
Fluorescence• Light Scattering• Imaging
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
KnowledgeKnowledge
• Monitoring multiple properties provides insights into areas and mechanisms that have not been investigated
What you know
What you don’t know
What you don’t know that you don’t know
Sentry Equipment CorpSentry Equipment CorpSampling Solutions • Specialty Heat Sampling Solutions • Specialty Heat ExchangersExchangers
SummarySummary
• Sampling is a critical part of process control and is often overlooked
• Indirect methods of sampling are the safest, yet most challenging
• The goal is to get representative samples• Material and process variations as well as
sampling techniques and tools effect our ability to get representative samples
• Understand the process and sampling objectives
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